what's the purpose of design patterns in Asp.Net

Design patterns are recognized solutions to common problems defined originally by the Gang of Four programmers. Design patterns are used throughout the ASP.NET Framework. The various patterns are commonly divided into several different groups depending on the nature of the design problem they intend to solve.

A design pattern is a general reusable solution to a commonly occurring problem within a given context in design. A design pattern is not a finished design that can be transformed directly into source or machine code. It is a solution to how to solve complex problems.